1. Field of the Invention
The present invention relates to a developer detection device capable of detecting a remaining amount of developer stored in an accommodating container, and a developer accommodating device, a developing unit and an image forming apparatus each including the developer detection device.
2. Description of the Related Art
In general, an electrophotographic image forming apparatus such as a printer, a photocopier, a facsimile and a multifunction peripheral (MFP), includes a developer detection device capable of detecting a remaining amount of developer (toner) stored in an accommodating container of a developing unit. For example, a developer detection device described in Japanese Patent Kokai Publication No. 2007-93663 (Patent Document 1) includes a light blocking plate for blocking light emitted from a light-emitting unit in accordance with the amount of toner in an accommodating container and detects that the amount of toner becomes less than a predetermined reference amount, i.e., the remaining amount of toner is small, on the basis of a light blocked period during which the light from the light-emitting unit is being blocked by the light blocking plate. See Patent Document 1 (e.g., Abstract, FIG. 2, FIGS. 6A and 6B, and FIGS. 7A and 7B).
However, since a stop position of the light blocking plate corresponding to the remaining amount of toner exhibits fluctuations, the stop position of the light blocking plate sometimes does not correctly correspond to the remaining amount of toner. In such a case, even if the remaining amount of toner stored in the accommodating container is small, the light blocking plate cannot appropriately block the light emitted from the light-emitting unit and part of the light emitted from the light-emitting unit enters a light-receiving unit, and therefore the remaining amount of toner cannot be correctly detected. Moreover, in the conventional device, since the light blocking plate is formed to be compact, part of the light emitted from the light-emitting unit tends to enter the light-receiving unit by reflection, scattering or diffraction at another member. Therefore, even if an actual remaining amount of toner becomes small, the light sometimes enters the light-receiving unit. Consequently, the conventional device sometimes can detect that the remaining amount of toner is small, but cannot detect it at other times, when the remaining amount of toner is small. As described above, there is a problem that the remaining amount of toner cannot be detected appropriately.